In-line magnetic particle collector



Feb. 18, 1969 o. M. BOYD, JR., ET

IN-LINE MAGNETIC PARTICLE COLLECTOH Filed June 21. 1965 wh Z 0 .d w i wW 7 M a I- V W m V n mm W M N 933 ,7

mwamt A ro/Mfrs United States Patent IN-LINE MAGNETIC PARTICLE COLLECTORDavid M. Boyd, Jr., Clarendon Hills, and Kenneth, 0.

Rockey, Evanston, Ill., assignors to Universal Oil Products Company, DesPlaines, Ill., a corporation of Delaware Filed June 21, 1965, Ser. No.465,404

US. Cl. 210-222 Claims Int. Cl. B01d /06; B03c 1/10 ABSTRACT OF THEDISCLOSURE A particle collector for removing magnetic particles from afluid stream comprising an outer casing and an inner non-magneticopen-ended conduit extending through the casing. A train of permanentmagnets is moved through the conduit, and the fluid stream is passedthrough the annular space between casing and conduit. The particles areattracted to the outer surface of the conduit and are swept therealongby the traveling magnetic field to'a particle collecting chamber whichis periodically emptied of stored particles.

This invention relates to apparatus for the separation of magneticparticles from a fluid stream. More particularly, the present inventionis directed to apparatus for effecting the continuous removal ofmagnetic particles from an acidic liquid stream.

In various chemical processes, the efiluent stream therefrom iscontaminated with small metallic particles comprising iron and/or nickelin suflicient quantity as to be susceptible to magnetic collection. Itis an object of this invention to provide means for purifying suchstreams by subjecting the particle-form contaminants to the action of atraveling magnetic field. Other objects and advantages of theinventionwill be made apparent hereinbelow.

In one embodiment this invention relates to a magnetic particlecollector comprising a casing adapted to contain a fluid stream; spacedfluid inlet and outlet means connecting with said casing; a non-magneticopen-ended conduit supported within said casing adjacent to said inletand outlet means, both ends of the conduit extending through the casingto the exterior thereof; a magnet train within said conduit comprisingan elongate carrier means and a series of permanent magnets carried :bysaid carrier means; and drive means coupled to said magnet train foreffecting movement thereof through said conduit.

A more specific embodiment of this invention is directed to a magneticparticle collector comprising an elongate shell adapted to contain afluid stream; longitudinally spaced fluid inlet and outlet meansconnecting with such shell; a non-magnetic open-ended conduit supportedwithin said shell opposite said inlet and outlet means and extendinglengthwise through the shell to the exterior thereof; a magnet traincomprising an endless belt-like carrier means adapted to travellongitudinally within said conduit in a forward direction and outside ofsaid conduit in the reverse direction, and a series of permanent magnetscarried by said carrier means substantially uniformly spaced along theentire length thereof; and rotary drive means operatively engaging saidcarrier means for effecting continuous unidirectional movement of themagnet train through the conduit.

The arrangement and operation of our invention are further described inconnection with the accompanying drawings in which:

FIGURE 1 is a sectional elevation view of the apparatus.

FIGURE 2 is an enlarged view of a section of the magnet train.

ICC

FIGURE 3 is a transverse view of the apparatus taken along line 3-3 ofFIGURE 1.

FIGURE 4 is a plan view of the apparatus taken along line 44 of FIGURE1.

With reference to FIGURE 1, the particle collector comprises an outerelongate shell or tube 10 having a fluid inlet conduit 11 and a fluidoutlet conduit 12 longitudinally spaced therefrom. An inner open-endedconduit or tube 13 is concentrically mounted within shell 10, extendinglengthwise the fulllength thereof. Annular gas ket or seal members 14,compressively inserted into each end of shell 10, serve as fluid-tightend closures for the shell as well as supporting the inner tube. Tube 13is constructed of a suitable non-magnetic material such as glass,plastic, aluminum, copper or stainless steel, selected with due regardto the corrosiveness, if any, of the process fluid being handled.

A magnet train, indicated generally by numeral 15, is arranged to movelongitudinally through tube 13. In a preferred embodiment of ourinvention, such magnet train comprises an endless elongate loop offlexible non-magnetic tubular woven braiding 16 and a series of spacedpermanent magnets 17 carried within the braiding, the magnets beingsubstantially uniformil spaced along the entire length of the braiding.Braiding 16 may be made of tinned copper, similar in construction toelectrical shielding braid, or other non-magnetic material such asaluminum, stainless steel or plastic. Magnets 17 may be in the form ofelongated cylinders with a diameter slightly greater than the insidediameter of braiding 16 when the latter is unstressed. As shown ingreater detail in FIGURE 2, the magnets are spaced approximately onemagnet length apart to increase the flexibility of the assembly and, aswill be explained below, are preferably arranged to have successivelyrepelling polarities, e.g., contiguous poles of any two adjacent magnetsbeing of like'polarity, either north or south. When the braiding isplaced under tension, as by engagement with mechanical drive means, thebraiding wall necks down between magnets as indicated at sections 16a ofFIGURE 2, thereb gripping the magnets and locking them in place withinthe braiding to limit or prevent any substantial movement of the magnetswithin the braiding.

The magnet train is engaged and driven by a pair of spaced pulleymembers or sheaves 19 and 20 disposed externally of shell 10 and inalignment with central conduit 13. Sheave 19 is a power sheave keyed tothe shaft of a combination motor-speed reducer 22 (FIGURE 4) mountedupon a pedestal 23. Sheave 20 is an idler or takeup sheave mounted on apedestal 21 which may be provided with through-bolted slots forregulating the tension imposed on the magnet train. The return run ofthe magnet train is taken through a lower external housing or guard tube24 designed to protect the magnet train from dirt, moisture and fallingobjects, as well as to furnish some support therefor. The shell 10 andtube 24 are supported in horizontal positions by suitable spaced framemembers 25.

A pair of eccentrically bored orifice plates 26 are transverselydisopsed across the interior of shell 10. These plates are located ashort distance beyond the fluid outlet conduit 12, away from the inletconduit, and serve as baffle means dividing the interior of shell 10into two functionally distinct chambers or zones; on the left, aparticle separation zone and, on the right, a fairly quiescent particlestorage zone. As shown in FIGURE 3, the, eccentric bore is somewhatlarger than the diameter of conduit 13 so that the latter, which extendscompletely therethrough, rests in tangential contact upon the lower edgeof the bore whereby to furnish additional support for conduit 13, andalso to provide open communication along the external surface of conduit13, via the crescent-shaped passageway 27, between the particleseparation zone and the particle storage zone. Also as shown in FIGURES1 and 3, each of plates 26 is provided with an upper gas vent hole 27aand a lower liquid back-flush hole 27b.

According to one particular application of our invention, the fluid tobe clarified is a liquid comprising a mineral acid such as HCl, H 50 orHNO at concentrations ranging from dilute to highly concentrated, inwhich there are suspended metallic impurities in the form of minutemetal particles, mainly colloidal agglomerates having a size of theorder of 1-100 microns, and typically comprising iron, nickel andcopper. In many cases, the particles themselves are attacked by the acidresulting in undesirable chemical contamination of the acid. Thereforethe present apparatus is designed not only to separate the maximumweight of metal particles per pass but also to remove them from contactwith the low pH region of the acid stream at a rapid rate.

With further reference to FIGURE 1, a feed stream comprising asuspension of minute magnetic metal particles in acid is charged toshell through inlet line 11. The stream flows through the annularparticle separation zone and clarified acid is taken out through line12. At the same time the magnet train is being driven from left toright, or cocurrently with the liquid flow, at a velocity which ispreferably substantially differente.g., greater than or less than thesuperficial liquid velocity within the separation zone; the superficialliquid velocity is defined as the average velocity across the annularspace between shell 10 and the tube 13, assuming perfect plug flow. Thereason for maintaining the difference in velocities will become apparentfrom a consideration of the nature of the magnetic field generated bythe magnet train. Looking for the moment at a single magnet 17, thefield thereof is roughly ellipsoidal in form, the lines of force curvingradially outward in all directions from one end of the magnet, cuttingthrough the wall of conduit 13 and curving out through the annularparticle separation zone and thence returning through the conduit Walland converging into the other end of the magnet. The field generated bythese series of magnets can be characterized as lobulate meaning aseries of coaxial ellipsoids or three-dimensional lobes spaced apart inthe direction of liquid flow and which cut through the conduit andproject transversely into the particle separation zone. By arranging themagnets so as to have alternately opposing polarities, as abovedescribed, the fields of adjacent magnets coact in a manner whichcompresses each field in the axial or longitudinal direction and pushesthe lines of force farther out in the radial direction; this in turnincreases the magnetic field strength in the particle separa tion zone,for a given magnet strength and central conduit diameter, over and abovethat which would be obtained by a random arrangement of magnets or apattern of mutually attracting polarities. By way of example, forconduit 13 outside diameters in the range of 0.5"2", field strengths of100-1000 gauss at the outside surface of conduit 13 can be obtainedutilizing commercially available alloy magnets. By maintaining asubstantial difference in velocities between the liquid flow and thelobulate magnetic field, each impurity particle will pass through anumber of lobes during its time of passage through the particleseparation zone and there is a high probability of capture. However, asthe relative velocity approaches zero, a given impurity particle willpass through fewer and perhaps no lobes, and the probability of captureis somewhat lower, resulting in reduced collection efficiency. The lowerlimit of field velocity is determined in accordance with the impuritycontent of the feed stream and the permissable residence time of themetal particles in the low pH region; obviously it should not be so lowas to result in excessive accumulation of particles in the separationzone. The upper limit of field velocity is fixed by the capability ofthe magnet train drive mechanism and tolerable wear and tear on themagnet train itself. It is preferred, therefore, that the velocity ofthe magnet train be substantially less than the superficial liquidvelocity; for example, very good results and very high collectionetficiencies can be realized when the linear velocity of the lobulatemagnetic field is maintained in the range of about 0.1-0.5 times thesuperficial liquid velocity within the separation zone. The maximumpermissible liquid velocity, in turn, is determined by the point atwhich the drag forces acting on the particles are so great so tosubstantially prevent their capture by the magnetic field; by way ofexample, for iron-nickel-copper particles in the size range of 1l000microns and a field strength of -600 gauss (existing midway between tube13 and shell 10) such maximum superficial liquid velocity will be of theorder of 25-125 feet per minute, depending, of course, on the densityand viscosity of the liquid stream and the dimensions of the particularapparatus.

The magnetic metal impurity particles, upon intercepting the travelingmagnetic field, are attracted to the outside or collecting surface ofconduit 13. The particles accumulate thereon in a film or thin layer 36.Because of the presence of hydrogen bubbles occluded by the particleagglomerates, there exist buoyancy forces acting upon the particles inopposition to the magnetic forces; therefore the layer 36 tends toaccumlate mainly on the upper surface of conduit 13, as illustrated inFIGURE 3. The traveling magnetic field simultaneously sweeps the layerof particles along the surface of conduit 13 from left to right inFIGURE 1, through openings 27 in orifice plates 26 and into therelatively quiescent particle storage zone defined by the right-handportion of shell 10 beyond plates 26. Upon reaching the right endwall14, the particles are blocked from further movement and so accumulatetherein. Hydrogen which may accumulate withinrthe particle storage zoneis released therefrom through upper vent holes 27a and eventually passesout of the apparatus through conduit 12. In certain instances it willbe. desirable to provide a holding magnet 32, either a permanent magnetor an electromagnet, disposed exteriorly and in close proximity to theshell 10, of sufiicient strength to overcome the traveling field,causing the particles to be.pulled away from conduit 13-, and into amass adhering to the shell wall. In such case, the end portion 10a ofthe shell will be fabricated of non-magnetic material and may be swageddown, as indicated in FIGURE l,-to increase the efiective strength ofholding magnet 32. In order to reduce the hydrogen ion concentration in-1the particle storage zone, and thereby to inhibit dissolution of themetal particles by the acid, a stream of water may be continuously orintermittently introduced into the storage zone through a backflush line28 and valve 29. The water backfiows through the storage zone andopenings 27, as well as through lower backfiush holes 27b, into theseparation zone and out through line 12. The quantity of water soinjected is quite small in relation to the quantity of acid treated inorder not to appreciably dilute the acid stream.

In some cases the amount of occluded hydrogen carried into the particlestorage zone may be quite substantial and it will be advantageous toprovide additional means for bleeding off the hydrogen trapped therein.This may be accomplished by a vertical standpipe 33 connecting at itslower end with the particle storage zone and terminating at its upperend in a gas disengaging tank 34. Hydrogen bubbles released from thestorage zone pass upwardly through pipe 33 and the resulting collectedhydrogen is vented through line 35. Line 35 may include a back pressurecontroller or may be connected to a separate external zone maintainedunder a regulated pressure somewhat less than the ambient pressurewithin the particle storage zone. The water inlet line may be connectedto the standpipe 33 if desired. The volume of water within pipe 33 andtank 34 may also be utilized to assist in the removal of metal particlesfrom the storage zone as explained below.

Ordinarily the volume of the particle storage zone will be sufficient toaccommodate from several hours to several days collection of particles.But to permit the elimination of particles from the storage zone asperiodically required when the storage area becomes full, there isprovided a particle drain line 30 with a valve 31. In combination withthis means, a short length of magnet train 15 contains one or morenon-magnetic dummies or spacers 18, of approximately the same size asmagnets 17, but which produce no magnetic field. When spacers 18 aremoved into transverse alignment with line 30, the magnetic field in thisregion is greatly attenuated and the metal particles gain relativelyfree mobility and freeflowing characteristics during the brief intervalthat spacers 18 occupy this position. Therefore, to discharge particlesfrom the storage zone, one merely waits until spacers 18 arrive oppositeline 30 (if holding magnet 32 is employed, its field is also cut off orremoved at this time) valve 29 is temporarily closed and valve 31 isbriefly opened. The metal particles are thereupon pressured out throughline 30 to a suitable drain. Also at this time the water stored withinstandpipe 33 may serve as a flushing medium to aid in the discharge ofparticles and also to minimize pressure fluctuations during the particledischarge cycle. The above-described discharge cycle may beautomatically programmed by suitable control apparatus including a cycletimer, solenoid valves and a magnet train position sensor.

Given below are typical specifications for a horizontal magneticparticle collector designed to handle 60-75 g.p.m. of HCl solution,recovering 65 grams per hour of magnetic metal impurities at acollection efliciency of 98 percent:

Outer shell 6'' ID. glass pipe.

onds once every 2 hours.

Our apparatus as described above preferably incorporates cocurrenttravel of the magnetic field relative to the direction of liquid flow.The invention may instead utilize countercurrent motion. This is lessdesirable, however, because then the highest concentration of particleagglomerates moving along the surface of conduit 13 occurs opposite theinlet line 11, and the relatively high turbulance at this point may tendto dislodge and scatter some of the particles. In some cases this may beavoided by using suitable baffling; frequently, however, the particlescarried by the inflowing stream are too fragile to withstand impact on abaffle plate and would disintegrate into colloidal sized particles nolonger susceptible to magnetic attraction.

Many variants in the above-described apparatus will be apparent to thoseskilled in the art and are embraced within the scope of our invention.With regard to the construction of the central conduit, this conduit,although preferably straight, may terminate in large radius bendsadapted to permit free movement of the magnets therethrough andextending through the sidewall of the outer shell. With regard to theconstruction of the magnet train, this may comprise a series of hollowcylindrical or sleevelike magnets, the centers of which are packed withwood,

plastic or other easily workable material into which hooks are screwedor otherwise inserted, the hooks engaging each other to link themagnetic sleeves together, thereby forming a train. Alternatively, themagnet train may comprise other belt-like carrier means such as aribbon, tape, belt or chain with the magnets fixedly attached thereto.Alternatively, the magnet train may take the form of a reciprocable roddriven by a pneumatic or hydraulic piston; such piston may have a dualspeed capability providing a slow speed for the forward or particlesweep stroke, and a high speed for the return stroke during which noappreciable sweeping action can occur. Our apparatus may be employed topurify gas, vapor or mixed phase streams as well as liquid streams, andmay be mounted in a vertical or inclined position as well as thehorizontal.

Where a larger capacity apparatus is desired, the magnetic particlecollector of our invention may comprise a plurality of magnet tubesmounted in parallel within a single shell in the manner of a shell andtube heat exchanger, with a magnet train running through each of saidtubes. An alternative arrangement is to provide a second shell aroundthe return run of the magnet train, e.g., in FIGURE 1 for example,around the guard tube 24, and to split the feed stream into two streams,one entering each shell. The relative motion of liquid flow and themagnetic field may be cocurrent in both shells, or countercurrent inboth shells, or cocurrent in one shell and countercurrent in the othershell.

The invention may be practiced by other types of apparatus. -Forexample, instead of a traveling train of permanent magnets, one mayutilize a series of stationary spaced electromagnets, disposed eitherwithin a central conduit or along the exterior of the outer shell,driven by a suitable timing circuit to provide a stepping magneticfield. In another form of apparatus, a series of permanent magnets maybe mounted around the rim of a rotating wheel, with the separationchamber comprising a hollow :arcuate shroud surrounding a portion of theperiphery of the wheel; a second magnet wheel rotating in the oppositedirection adjacent to the first wheel may be used to pick up theparticles collected in the shroud and sweep them through a back-flushedconduit to a storage chamber.

We claim as our invention:

1. A magnetic particle collector comprising:

( 1) a casing adapted to contain a fluid stream;

(2) spaced fluid inlet and outlet means connecting with said casing;

(3) a non-magnetic open-ended conduit supported within said casingadjacent to said inlet and outlet means, both ends of the conduitextending through the casing to the exterior thereof;

(4) a magnet train within said conduit comprising a series oflongitudinally arranged permanent magnets constructed and arranged totravel in unison therethrough;

(5) drive means coupled to said magnet trains to effect movement thereofthrough said conduit;

(6) means defining a particle collection zone within said casing; and

(7) means to remove particles from said collection zone.

2. The apparatus of claim 1 further characterized in that said casingcomprises an elongate shell, said fluid inlet and outlet means arelongitudinally spaced with respect to said shell, and said open-endedconduit extends lengthwise through said shell.

3. The apparatus of claim 2 further characterized in that said magnettrain comprises an endless belt-like carrier adapted to travellongitudinally within said conduit in a forward direction and outside ofsaid shell in the reverse direction, said magnets being carried by andsubstantially uniformly spaced along the length of the carrier.

4. The apparatus of claim 3 further characterized in that said drivemeans is 'a rotary drive means operatively engaging said carrier andeffecting continuous unidirectional movement of said magnet trainthrough said conduit.

5. A magnetic particle collector comprising:

(1) an elongate shell adapted to contain a fluid stream;

(2) a fluid inlet line connecting with one end portion of said shell, aparticle drain line connecting with the other end portion of said shell,and a fluid outlet line conecting with an intermediate portion of saidshell;

(3) transverse perforate bafile means mounted within the shell betweensaid fluid outlet line and said particle drain line to define a particlecollection zone in said other end portion of said shell;

(4) a non-magnetic, substantially straight, open-ended conduit supportedwithin said shell opposite said inlet and outlet lines and said drainline and extending lengthwise through said baffie means and said shelland both ends thereof;

(5) a magnet train within said conduit comprising a series oflongitudinally arranged permanent magnets constructed and arranged totravel in unison longitudinally through said conduit in a forwarddirection and outside of said shall in the reverse direction; and

(6) drive means operatively engaging said magnet train for effectingcontinuous unidirectional movement thereof through said conduit.

6. The apparatus of claim 5 further characterized in that said perforatebaffle means comprises a plurality of longitudinally spaced platemembers.

7. The apparatus of claim 5 further characterized in that a baclcfiushline connects with said other end portion of said shell.

8. The apparatus of claim 5 further characterized in that said magnettrain comprises an endless loop of flexible non-magnetic tubularbraiding maintained under tension, said magnets being carried within thetubular braid ing and gripped by the braiding wall under tension wherebyto inhibit displacement of the magnets relative to the braiding and saidmagnets being substantially uniformly spaced along the length thereof.

9. The apparatus of claim 8 further characterized in that a short lengthof said tubular braiding includes at least one non-magnetic spacermember instead of a magnet.

10. The apparatus of claim 5 further characterized in the provision ofmeans to vent gas from said particle collection zone.

11. The apparatus of claim 5 further characterized in that saidopen-ended conduit is formed of stainless steel.

12. The apparatus of claim 5 further characterized in that a holdingmagnet is disposed exteriorly of said shell close to the wall thereofand adjacent to said other end portion of the shell.

'13. The apparatus of claim 5 further characterized in that a shortlength of said magnet train includes at least one non-magnetic spacermember instead of a magnet.

'14. The apparatus of claim 5 further characterized in that saidperforate bafile means comprises at least one eccentrically boredorifice plate, the bore thereof being of larger size than said conduit,and the conduit extending through the bore in contact with a portion ofthe perimeter of the bore.

15. The apparatus of claim 5 further characterized in that said seriesof magnets are arranged so that adjacent poles of any two adjacentmagnets are of like polarity.

References Cited UNITED STATES PATENTS 453,317 6/1891 Townsend 2 10-222X 2,688,403 9/ 1954 Anderson 210222 2,717,080 9/1955 Anderson 210-2222,759,606 8/1956 Nippert 210222 3,121,683 2/1964 Fowler 210-223 FOREIGNPATENTS 1,128,821 5/ 1962 Germany.

151,749 7/1962 U.S.S.R.

REUBEN FRIEDMAN, Primary Examiner.

W. S. BRADBURY, Assistant Examiner.

U.S. Cl. X.R.

